fix: prevent delete if animal type is still being referenced

src/wuttafarm/db/model/asset_animal.py

@@ -80,6 +80,14 @@ class AnimalType(model.Base):
         """,
     )
 
+    animal_assets = orm.relationship(
+        "AnimalAsset",
+        doc="""
+        List of animal assets of this type.
+        """,
+        back_populates="animal_type",
+    )
+
     def __str__(self):
         return self.name or ""
 
@@ -103,6 +111,7 @@ class AnimalAsset(AssetMixin, EggMixin, model.Base):
         doc="""
         Reference to the animal type.
         """,
+        back_populates="animal_assets",
     )
 
     birthdate = sa.Column(

src/wuttafarm/web/views/animals.py

@@ -106,6 +106,19 @@ class AnimalTypeView(AssetTypeMasterView):
 
         return buttons
 
+    def delete(self):
+        animal_type = self.get_instance()
+
+        if animal_type.animal_assets:
+            self.request.session.flash(
+                "Cannot delete animal type which is still referenced by animal assets.",
+                "warning",
+            )
+            url = self.get_action_url("view", animal_type)
+            return self.redirect(self.request.get_referrer(default=url))
+
+        return super().delete()
+
     def get_row_grid_data(self, animal_type):
         model = self.app.model
         session = self.Session()